The present device relates to a watertight sealing lip for enhancing the watertightness of a grommet by which the gap between a wall of a panel or the like and an electric wire extending through the hole of the wall is sealed in a watertight manner.
When the electric wire 1 of a motor vehicle or the like is inserted through a dashboard 2, a grommet is used to seal the gap between the electric wire and the dashboard, as shown in FIG. 1.
One example of a grommet is proposed in the Japanese Utility Model Application No. 192423/86 (filed on Dec. 16, 1986 and published on Jun. 28, 1988) which is assigned to the present assignee and which comprises a soft body A and a hard resin member B as shown in FIG. 2. The body A of the grommet comprises a tube 4 having a plurality of lips 3, which elastically pinch an electric wire 1 to seal it, an annular plate 5 extending continuously to the tube, and a cylindrical portion 6 extending continuously to the outer circumferential edge of the annular plate. An annular holding portion 7 extends inward from the end of the cylindrical portion 6. An annular watertight sealing lip 8 obliquely extends outward from the end of the cylindrical portion 6. An inner lip 9 curves from the end of the holding portion 7. The butt 10 of the hard resin member B of the grommet is fitted in an opening defined by the annular plate 5, the cylindrical portion 6 and the holding portion 7. An engaging portion 12 is provided at the end of a cylindrical portion 11 extending continuously to the butt 10 of the hard resin member B. Shown at 13 in FIG. 2 is a watertight sealing projection 13 provided on the watertight sealing lip 8. When the body A of the grommet is combined with the resin member B engaged on a wall 2 of a panel or the like, the tip of the watertight sealing lip 8, the watertight sealing projection 13 and the tip of the inner lip 9 are elastically deformed into tight contact with the wall 2, the wall can be sealed by the grommet body A of elasticity.
However, if there is a projecting piece such as foreign matter 14 on the surface of the wall 2 as shown in FIG. 3A, the projecting piece separates the watertight sealing projection 13 from the wall 2 creating an opening between the wall and the watertight sealing projection and keep the tip 8a of the watertight sealing lip 8 off the wall to let water come in.
Further, if the tip 8a of the watertight sealing lip 8 is defective at the time of the attachment of the grommet to the wall 2, as shown in FIG. 3B, the watertight sealing projection 13 is separated from the wall 2 to let water enter thereinto.
The present device is made in order to solve such problems.
According to the present device, a watertight sealing lip is provided for a grommet which tightly seals the gap between a wall of a panel or the like and an electric wire extending through the wall. The watertight sealing lip is annular and obliquely extends from the end of the cylindrical portion of the grommet toward the wall so that the tip of the lip comes into contact with the wall. The side of the watertight sealing lip, which faces the wall, is provided with a plurality of watertight sealing projections which extend in the circumferential direction of the lip and whose cross sections are sequentially enlarged from the tip of the lip toward the end of the cylindrical portion of the grommet.
The watertight sealing lip of a conventional grommet is more flexible at and near the tip of the lip than at and near the end of the cylindrical portion of the grommet according to the invention so that the lip is more easily deformed into tight contact with a wall or a projecting piece on the surface of the wall, at and near the tip of the lip than at and near the end of the cylindrical portion of the grommet. However, the pushing force of the watertight sealing lip to the wall is weaker in the vicinity of the end of the cylindrical portion of the grommet than in the vicinity of the tip of the lip so that the lip does not come into tight contact with the wall near the end of the cylindrical portion of the grommet.
The watertight sealing lip provided in accordance with the present device has the plurality of watertight sealing projections which are made sequentially larger in size toward an end of a cylindrical portion of the grommet to sequentially increase the pushing forces of the watertight sealing projections to the wall and are disposed so that the projection of larger size is located on the part of the watertight sealing lip, the quantity of elastic deformation of which is smaller. For that reason, at least one of the watertight sealing projections comes into tight contact with the wall. The reliability of the watertight sealing function of the grommet is thus made high.